The two-and-a-half year period in which the Marine Corps' Infantry Officer Course became gender-integrated for research will end without a single female graduate.

The final two participants in the Marines' experiment with training women for ground combat started and failed the IOC on April 2. One was a volunteer, and the other was a member of the newly integrated ground intelligence track.

Both were dropped during the grueling initial endurance test, said Capt. Maureen Krebs, a spokeswoman for Headquarters Marine Corps. Nine of the 90 men who began the course were also cut.

The course, held quarterly at the Marine Corps Base in Quantico, Va., began accepting female officers fresh out of training in September 2012, as part of a larger research effort into the feasibility of opening ground combat jobs to women.

Lieutenants who made it through the legendarily 86-day course wouldn't receive an infantry military occupational specialty or career advancement. They did it only for the challenge and the hope of being part of a Marine Corps achievement.

But as the research continued, few volunteers took advantage of the opportunity. By July 2014, only 20 female officers had attempted the course. Only one made it through the combat endurance test, and none made it to the end.

Volunteers dwindled

To achieve their goal of 100 female volunteers cycling through IOC, the Marine Corps opened the course to female company-grade officers in October 2014, making hundreds more Marines eligible for the course.

The Corps also began requiring volunteers to get a first-class score on the male version of the service's physical fitness test, in an effort to better prepare them for the rigors of IOC.

The effort was a mixed success. In the October iteration of IOC, three of the seven female volunteers made it through the combat endurance test, bringing the total number of women to pass the test to four. Two of those who passed the test were captains from the fleet.

As time passed, no influx of volunteers materialized.

The testing period ends with just 27 female volunteers having attempted the course. Two other female officers tried it as part of required ground intelligence officer training. That occupational specialty was opened to female officers in late 2013, with IOC as a qualification requirement for applicants.

None of the 29 female officers made it to the end of the course.

Looking ahead

While IOC is closing to volunteers, female applicants for ground intelligence officer positions will continue to attend the course, Krebs said.

Officials have said ongoing research will consider many aspects of temporarily integrating IOC, including the number of volunteers, their pass rate and performance in the course. That data will be taken alongside other research points, including the much higher success rate for enlisted female Marines in passing the Infantry Training Battalion course at Camp Lejeune, North Carolina.

When that research concluded earlier this year, 240 women had attempted the course, with a pass rate of 44 percent.

Also considered will be data generated from the Ground Combat Element Integrated Task Force, which is conducting assessments with male and female troops in a variety of infantry specialties now on the West Coast.

All of that information will be compiled this summer and used for Commandant Gen. Joseph Dunford's recommendation to the secretary of defense on whether to open remaining ground combat units to female troops. A decision is expected from the Pentagon early next year.